Conservation of Dry Forest Old Growth in Eastern Oregon

Conservation of old-growth forests has become an increasingly important objective of Forest Service managers over the last three decades. The US Forest Service recently made changes to policies that prohibit cutting of live trees >53 cm (the “21-inch rule”). We review the disturbance ecology of dry and mesic old-growth forests of Oregon and contrast conservation policies for these two forest types. We describe the development of age-based alternatives to the 21-inch rule on the Klamath Reservation and in the Malheur National Forest in eastern Oregon. We conclude by outlining an adaptive management strategy to conserve dry forest old growth that seeks to restore the ecological processes that perpetuate old tree populations over time. We argue that what is good for dry forest ecosystems is good for dry forest old growth, especially in the face of changing climate and disturbance regimes. Study Implications: Age-based limits are a viable alternative to the size-based limits that the U.S. Forest Service has been using to conserve old growth in dry, fire-prone forests of eastern Oregon. Another alternative is a process-based approach that emphasizes restoring processes, including frequent fire that make old-growth trees resistant to a warmer and more fiery future. Multiscale inventories that track the abundance and distribution of trees of different species, sizes, and ages can inform tree conservation priorities and assess progress towards desired outcomes. Robust monitoring programs can facilitate collaborative data-driven adaptation at the local level and improve dry forest old-growth conservation outcomes.